A gravity molding device for molding a product by pouring a molten metal only due to gravity of the molten metal into a mold from a pouring gate provided at an upper portion of the mold can increase a cooling rate at the time of molding, and can produce a precise molded product excellent in a molded surface and dimension accuracy. The product is excellent particularly in pressure resistance and mechanical property. However, the gravity molding device requires that a riser for compensating decrease in volume of the molten metal at the time of solidification be formed at an upper portion of the molded product, and that a period of time to cool and solidify the riser be secured in addition to a period of time to solidify the molded product. Further, the formation of the riser needs more amount of the molten metal and higher cost of melting, and also needs extra process cost of cutting the riser. In addition, in order to obtain the molded product having no shrinkage cavity, the molten metal needs to be directionally solidified toward the riser from a bottom side of a space in the mold. However, the mere formation of the riser does not solve a problem in that solidification timing of the molten metal cannot be controlled sufficiently.
In this context, as illustrated in FIG. 10, the inventor of the subject application proposes a tilt type gravity molding device 100 including a closing portion 102 capable of opening/closing a sprue runner 101, and a gas supplying section 104 capable of supplying gas into a product forming space 103 (Patent Literature 1). In the tilt type gravity molding device 100, after pouring a molten metal 105 into the product forming space 103, the closing portion 102 that slides horizontally closes the sprue runner 101, and the gas supplying section 104 supplies the gas into a mold 106. In this way, the molten metal 105 contained in the mold 106 can be pressurized by the gas. The tilt type gravity molding device 100 pressurizes the molten metal 105 by the gas into the product forming space 103 in the mold 106, and thus causes no shrinkage cavity and no crack even in a case where the riser is not substantially provided. Therefore, the tilt type gravity molding device 100 does not need the period of time to cool and solidify the riser, and thus can shorten a cycle of a molding time period and reduce manufacturing cost of the molded product. Further, the tilt type gravity molding device 100 can provide effects of reducing an amount of the molten metal for forming the riser, cost of melting, and process cost of cutting the riser.